1. Field of the Disclosure
The present invention relates to pressure actuated switching devices and a method for making them.
2. Description of the Related Art
Pressure actuated switching devices are known in the art. Typically, such devices include two spaced apart conductive layers enveloped in an insulative outer cover. Optionally, the conductive layers may be separated by an insulative spacer element, or xe2x80x9cstandoff.xe2x80x9d Also, the pressure actuated switching device can optionally include a piezoresistive material. The electrical resistance of a piezoresistive material decreases in relation to the amount of pressure applied to it. Piezoresistive materials provide the pressure actuated switching device with an analog function which not only detects the presence of a threshold amount of applied force but also provides a measure of its magnitude. Pressure actuated switching devices can be used as mat switches, drape sensors, safety sensing edges for motorized doors, and the like.
U.S. Pat. Nos. 6,121,869 and 6,114,645 to Burgess disclose a pressure activated switching device which includes an electrically insulative standoff positioned between two conductive layers. The standoff is preferably a polymeric or rubber foam configured in the form of contoured shapes having interdigitated lateral projections. Optionally the switching device can include a piezoresistive material positioned between a conductive layer and the standoff.
U.S. Pat. No. 5,856,644 to Burgess discloses a freely hanging drape sensor which can distinguish between weak and strong activation of the sensor. The drape sensor includes a piezoresistive cellular material and a standoff layer. The drape sensor can be used in conjunction with moving objects such as motorized doors to provide a safety sensing edge for the door. Alternatively, the drape sensor can be used as a freely hanging curtain to detect objects moving into contact therewith.
U.S. Pat. Nos. 5,695,859, 5,886,615, 5,910,355, 5,962,118 and 6,072,130, all to Burgess, disclose various embodiments of pressure activated switching devices.
As demand grows for lower cost high performance pressure actuated switching devices it becomes increasingly advantageous to have more efficient and more flexible methods of production. For example, it may be preferable to have one or more components fabricated more efficiently at one facility or operation, then shipped to another facility or operation for further processing and/or assembly. These and other advantages are provided by the method for making a pressure actuated switching device described below.
A method is provided herein for making a pressure actuated switching device. The method comprises the steps of: (a) providing a first substrate having a first surface; (b) providing a transfer substrate having a release surface; (c) applying a conductive coating to the release surface of the transfer substrate; (d) contacting the conductive coating with the first surface of the first substrate under conditions of heat and pressure sufficient to cause the conductive coating to transfer from the release surface of the transfer sheet to the first surface of the first substrate; and (e) positioning the first substrate in juxtaposition with a second substrate.